I have a Dell optiplex Gx520 adn wish to change the DVD ROM for a DVD R/W. Where do I start as I cannot find any release screws? littleal

There's a latch of the rear-top, just hold and press (as you open and car door), the case will fling out.
You can refer to this video... (not the exact model, but more or less similar)
I hope you know how to replace the CD-Rom drive. If you need further help, let me know.

Good luck.

Thanks for using FixYa.

1. If you are installing a new drive:
   
   
   1. Press the two snaps on the top of the drive-panel insert and rotate the insert toward the front of the computer.
      
      
   1. Remove the three shoulder screws from the drive-panel insert.
      
      
2. If you are replacing an existing drive:
   
   
   1. Press the two snaps on the top of the drive-panel insert and rotate the insert toward the front of the computer.
      
      
1. Remove the three shoulder screws from the existing drive.
   
   
2. Insert the three shoulder screws into the sides of the new drive and tighten them.